Viscosity-stabilized foam precursors and process

ABSTRACT

STABILIZED LIQUID NON-POLYMERIC FOAM PRECURSORS ARE PRODUCED WHEN FLUORINE SUBSTITUTED ALKANES BOILING ABOVE 60*F. ARE ADDED TO A LIQUID NON-POLYMERIC FOAM PRECURSOR PREPARED BY MIXING A POLYFUNCTIONAL AROMATIC CARBOXYLIC ACID DERIVATIVE WITH A LIQUID POLYARYLPOLYISOCYANATE. THESE FOAM PRECURSORS ARE REACTED WITH A POLYOL HAVING A MOLECULAR WEIGHT BELOW 2,000 AND CONTAINING AT LEAST THREE HYDROXYL GROUPS. THE RESULTING FOAMS PRODUCED ARE USEFUL FOR INSULATION OF WALLS, FOR FIREPROOFING BUILDINGS AND THE LIKE.

United States Patent Oflice 3,563,908 Patented Feb. 16, 1971 3,563,908VISCOSITY-STABILIZED FOAM PRECURSORS AND PROCESS Fred W. Koenig,Highland, and Stanley T. Kus, Griffith,

Ind., and Sheldon Howard Marcus, Skokie, Ill., assignors to Standard OilCompany, Chicago, Ill.

N Drawing. Continuation-impart of application Ser. No. 420,801, Dec. 23,1964. This application Dec. 22, 1967, Ser. No. 692,719

Int. Cl. C08g 22/44; C09k 3/00 US. Cl. 252182 Claims ABSTRACT OF THEDISCLOSURE This application is a continuation-in-part of Ser. No.420,801, filed Dec. 23, 1964, now abandoned, by the same inventors, FredW. Koenig, Stanley T. Kus and Sheldon H. Marcus.

This invention relates to improved stable foam precursor compositionsand to a process for stabilizing these compositions. In a particularaspect it relates to the stabilization of polyfunctional aromatic acidand polyarylpolyisocyanate compositions with fluorine containing loweralkanes. These stabilized compositions are then reacted with a polyolcontaining at least three reactive hydroxyl groups to produce thermallystable foam. The foams are useful in insulation of walls, forfireproofing buildings and the like. The resulting foams have greatcommercial value because they can be easily processed; for example, theydo not have to be prefabricated but can be prepared and foamed at theplace and in the position where they are to be used.

In the prior art fluorine containing lower alkanes were used as blowingagents for preparing polyurethane foam. In the prior art fluorinecontaining lower alkanes have not been used to stabilize liquidnonpolymeric foam precursors consisting of polyarylpolyisocyanate andpolyfunctional aromatic acids, anhydrides and acyl halides. Thefluorocarbon effectively prevents the solidification of the liquidnon-polymeric foam precursors by inhibiting the reaction between theanhydride and carboxyl or acyl halide groups with the isocyanato groups.

The foam precursors formed by solubilizing polyfunctional aromaticacids, acid anhydrides or acyl halides in polyarylpolyisocyanate asdisclosed in Ser. No. 420,774, filed Dec. 23, 1964, and now abandoned,are not very stable over long periods of time. The instability ismanifested by an increase in the viscosity of the foam precursorcomposition to a point where the mixture cannot be pumped and wherecommercial foam equipment cannot be used. This is apparently aconsequence of the tendency of the foam precursor to undergo furtherreaction with the resulting increase in viscosity, which tends to limitthe commercial utility.

It has been discovered that when a fluorocarbon is added to a mixture ofpolyfunctional aromatic acid, aromatic anhydride, acyl halide, or acombination of these are mixed with a polyarylpolyisocyanate, theresulting composition is stabilized for many months.

THE STABILIZATION SYSTEM The components of the stabilized system arefluorocarbon, polyarylpolyisocyanates and polyfunctional aromatic acids,acid anhydrides, acyl halides or mixtures of these. The polyfunctionalaromatic acid derivatives useful in making the flame-resistant foam havea polyfunctional aromatic nucleus substituted by the same or differentmembers selected from the group comprising carboxyl, acid anhydride oracyl halide. Non-reactive substituents may be present on the aromaticnucleus; for example, alkyl groups containing one to four carbon atoms,nitro groups and halide groups. Illustrative polyfunctional aromaticcarboxylic acid derivatives useful in our process are trimellitic acidanhydride, trimellitic acid, double anhydride of trimellitic acid,trimellitic acid halide, pyromellitic dianhydride, pyromellitic acid,terephthalic acid, phenylindane dicarboxylic acid, phthalic acid,phthalic anhydride, isophthalic acid, trimesic acid,3,4,3,4'-tetracarboxybenzophenone, 3,4,3 tricarboxybenzophenone,4,4-carboxybenzophenone, the acyl halides of these carboxybenzophenones,the dianhydride of 3,4,3,3-tetracarboxybenzophenones the monoanhydrideof 3,4,3,4-tetracarboxybenzophenone 1,3,3-trimethyl-1-phenylindane-4,6-dicarboxylic acid, and mixtures of these various carboxylic acidderivatives. The 4-trimellitate bis anhydride formed when trimelliticanhydride is reacted with a. polyol as disclosed in US. Pat. No.3,183,248, by Arthur G. Hirsch et a1. is also useful. These compoundshave two trimellitic acid anhydride groups joined through the carboxylicacid positions by ester linkages. These ester linkages can be joined byan alkylene group. Compounds joined by an ethylene or propylene groupare representative of this type of a compound. In case the esterlinkages are joined by propylenes the middle carbon can have an organicacid or ester attached to it without losing effectiveness in ourprocess.

To a degree the unique flame-resistance of the foam prepared from theliquid non-polymeric foam precursors can be attributed to these aromaticcompounds in the foam precursor.

The foam is not flame-resistant when the polyfunctional aromatic acidderivatives are left out from the foam precursor. Also when liquidnon-polymeric foam precursors are prepared using aliphatic anhydrides oracids, the resulting foams have a very high burning Weight loss, and inmany instances support a flame. Therefore, it is imperative thataromatic compounds be used. The best results are obtained with compoundshaving an anhydride group and also a carboxyl group or an acyl halidegroup. The preferred polyfunctional aromatic acid derivatives aresubstituted benzenes where one substituent is an anhydride and the otheris a carboxylic acid, acyl halide or an anhydride; trimelliticanhydride, the acid chloride of trimellitic anhydride, pyromelliticdianhydride and phthalic anhydride are good examples. Excellent resultsare, however, obtained with other aro, matic acids. For example, whentrimesic acid, terephthalic acid, phenylindane dicarboxylic acid aremixed with polyarylpolyisocyanate to form the non-polymeric liquid foamprecursor which is then reacted with a polyol having at least threereactive hydroxyl groups and a molecular weight below 2,000 give foamswhich have very low burning weight losses and have excellent thermalresistance. Good flame-resistant foams are also obtained when a liquidnon-polymeric foam precursor is prepared from a mixture of the acid, oranhydrides, is used. In many cases the foam precursor prepared fromthese mixtures shows a lower burning weight loss than when only purearomatic acids or anhydrides: are utilized.

The polyarylpolyisocyanates useful in this process contain at least twoaromatic rings with one isocyanato 3 group in each aromatic ring. Thesearomatic rings are suitable interconnected by ether, sulfonc, sulfoxide,methylene, propylene or a carbonyl linkage or by two methyl groupsconnected to a benzene ring substituted by an isocyanato group. Thepolyarylpolyisocyanates which are isocyanate-substituted biphenyls arealso useful in this process. In all of these cases the aromatic rings ofthe polyarylpolyisocyanates can be substituted by methyl, ethyl orpropylene groups. Specific examples of suitable polyarylpolyisocyanatesfor use in the invention include: polymethylene polyphenylisocyanatehaving from two to ten benzene rings each substituted by one isocyanatogroup and liquid mixtures at room temperatures of polymethylenepolyphenylisocyanates and one or more of the followingpolyarylpolyisocyanates: 4,4-diphenylmethylene diisocyanate;3,3'-diphenylmethylene diisocyanate; diphenyl diisocyanate;diphenylsulfone diisocyanate; di phenyl sulfide diisocyanate;diphenylsulfoxide diisocyanate; and diphenylpropane diisocyanate.Polymethylene polyphenylisocyanates having an average benzene ring Ithas been observed that the viscosity of the aromatic acids or aromaticacid derivatives and polyarylpolyisocyanate composition increased uponstanding. This increase in viscosity is highly undesirable whencarboxylic acid derivative and the polyarylpolyisocyanate compositiongets too viscous for commercial foam machine handling. It has beendiscovered that the addition of fluorocarbon stabilizes the liquidnon-polymeric foam precursor and thus removes an obstacle to theirsuccessful commercial utilization. It is believed that the fluorocarbons inhibit the further reaction between the isocyanato groups andthe anhydride, acyl halide or carboxylic acid group of the aromatic acidderivatives. The addition of a fluorocarbon to thepolyarylpolyisocyanates or to the aromatic acid, acid anhydride, acylhalide or to the foam precursor immediately after the ingredients aremixed, greatly increases the stability of the resulting liquidnon-polymeric foam precursor and in fact at least doubles the commercialuseful lifetime of these nonpolymeric foam precursors.

Fluorocarbons useful in the stabilization system are fluorinesubstituted lower alkanes having a carbon chain length not in excess ofsix carbon atoms and boiling above 60 F. and the fluorine substitutedcompounds can suitably be substituted by other halogen substituents.Representative fluorocarbons useful in stabilizing foam precursors aretrichlorofluoromethane; 1,1,2,2-tetrafluoro 1,2-dibromoethane;1,1,2-trifluoro,2,2-trichloroethane; 1,1,2,2-tetrachloro-1,Z-difluoroethane.

The mixing of the fluorocarbons, polyarylpolyisocynates andpolyfunctional aromatic carboxylic acid derivatives must be conducted ata temperature below the boiling point of the fluorocarbon. The mixing isconducted without any addition of external heat or pressure to thesystem and it is preferably conducted at room temperature.

The exact chemical mechanism for the foam precursor stabilization is notknown but it has been established that it is not the diluent effect ofthe fluorocarbon which is responsible for the decreased viscosity. Ithas been determined experimentally that when fluorocarbon is added tothe polyfunctional aromatic acid derivative or thepolyarylpolyisocyanate or the foam precursor and then the foam precursoris kept standing for about one Week, the viscosity increases slightly,up from 7.7 to 16 kilocentipoises. When the same identical mixture iskept for seven days without the fluorocarbon being added and thefluorocarbon is added immediately before taking the viscositymeasurement to equalize any diluent effect, we note that the viscosityis increased to 31 kilocentipoises. The same effect was observed when inanother experiment it was shown that for unstabilized mixtures theviscosity increased 156 kilocentipoises while the stabilized mixtureswent only up to 12 kilocentipoises. Thus, the stabilization effect in 16to 17 days was 144 kilocentipoises. This indi cates that the reactionbetween the isocyanato group and the carboxylic acid, acid anhydride oracyl halide groups is blocked or inhibited by the presence offluorocarbon while the diluent effect of the fluorocarbon is onlyslight.

The fluorocarbon can be added at any time either after thepolyfunctional aromatic carboxylic acid derivative and thepolyarylpolyisocyanate are mixed or to one of the components before itis mixed to form the foam precursor. In the preferred method thefluorocarbon is added to the polyfunctional aromatic acid derivative orpolyarylpolyisocyanate which is then mixed with the other component.

The ratio of the polyarylpolyisocyanate to the carboxylic acid or itsderivatives varies widely. The range is determined by the solubilitycharacteristics of the carboxylc acid derivatives in the variouspolyarylpolyisocyanates and the resultng compositions .amenability tomachine handling.

Usually the molar ratio of the acid derivative to thepolyarylpolyisocyanate varies from 1:5 to 4:5; the variation can,however, be greater (as shown in Example II hereinafter) and it is notnecessary that all of the acid or its derivatives be completelydissolved in the polyaryl polyisocyanate. All of these foam precursorcompositions are stabilized for several months when they contain atleast about 1% by weight of the fluorocarbon. To stabilize the foamprecursor for longer periods of time more fluorocarbon is added. Thepreferred range, however, is five to seven percent and the maximum isabout twenty percent.

In a preferred process ten percent by weight of trichlorofluoromethane.was added to a foam precursor composition made by solubilizing fortyparts of trimellitic anhydride in one hundred parts of polymethylenepolyphenylisocyanate. The viscosity of the resulting composition 'was7.7 kilocentipoises. After storage for one week the viscosity was 16kilocentipoises which is about one-half the viscosity of theunstabilized foam precursor. This viscosity is suflicient for handlingby commercial foam equipment. All of the stabilized foam precursorcompositions can be used in commercial foam equipment.

The stable foam precursors are usually stored at room temperature but toextend the life time of the foam precursor it is preferred, in someinstances, to store the stable foam precursors at temperatures of 0 to60 F.

The following examples are included as illustrations for thestabilization of foam precursors and for the preparation of fluorocarboncontaining precursors.

Example I Forty grams of trimellitic anhydride were solubilized in g. ofpolymethylene polyphenylisocyanate having a molecular Weight of 400, anequivalent weight of and a functionality of 3. To this composition 10 g.of trichlorofluoromethane were added. The viscosity at the time ofstorage was 7.7 kilocentipoises as measured on a Brookfield Viscometer.This composition was stored for seven days and the stability wascompared to an identical polymethylene polyphenylisocyanate-trimelliticanhydride composition to which 10 g. of trichlorofluoromethane wereadded just before the viscosity measurement was taken. The results ofthis experiment are seen in Table I which illustrates the stability ofthe foam precursor composition to which a fluorocarbon has been added.

Viscosity in kilocentipoises Polymethylene polyphenyl- Polymethyienepolyphenisocyanate, trimellitic acid yiisocyanate, trimellitic anhydridestored, triacid anhydride stored, triohlorofiuoromethane addedchlorofluoromethane added Storage time (days):

Example II One hundred grams of trimellitic anhydride are solubilized in89.3 grams of polymethylene polyphenylisocyanate having a molecularweight of 400, an equivalent weight of 140 and a functionality of 3. Tothis composition 35 grams of trichlorofiuoromethane were added. A stablecomposition is formed which is pumpable and can be used in commercialfoam equipment.

In a similar manner the other aromatic acid, acid anhydride or acylhalide and polyarylpolyisocyanate compositions disclosed above arestabilized to make them amenable to processing in commercial foamequipment.

In Example III varying amounts of trichlorofiuoromethane are used tostabilize the foam precursor by adding the trichlorofiuoromethane to thefoam precursor after the polymethylene polyphenylisocyanate having amolecular weight of 470, an equivalent weight of 140 and a functionalityof 3:3 to 3:3.

Example III One hundred grams of polymethylene polyphenylisocyanatehaving a molecular weight of 400, an equivalent weight of 140 and afunctionality of 3 were mixed with 55 grams of trimellitic acidanhydride. To this foam precursor were added the amounts oftrichlorofluorofit methane indicated in Table II. The amount oftrichloro- TABLE 11 Amount. of trichlorofluoromethane added to foamprecursor composition consisting of 100 grams polymethylenepolyphenylisocyanate and grams of trimellitie acid Days Centi- DaysCentianhydride aged poises aged poises The foregoing example illustratesthe effectiveness of trichlorofiuoromethane in stabilizing foamprecursors. It can be seen from the column indicating aging of 0 daysthat the incremental dilution effect between the two concentrationlevels contribute 2,000-5,000 centipoises lower viscosity initially butwhen looking at the column indicating aging for 76 days shows avariation between the concentration levels and viscosity of between10,000 to 150,000 centipoises.

Example IV One hundred grams of polymethylene polyphenylisocyanatehaving a molecular weight of 340, an equivalent weight of 132 and afunctionality of 2:5 to 2:7 were mixed with the acid derivativedescribed in Table III.

To the foam precursor then were added 20 grams oftrichlorofiuoromethane.

TABLE III Amount added in Poiytunctionul aromatic acid derivative gruntsRunNo Tcreph thalic acid 2 lsophthalic acid 48 3 Tilmesic acid 40 4.Benzophenone tetracarboxyiic dianh dri H2 5 4-acid chloride oftriinellitic nniiydri e n5 6 'lrimusic unhydride 55 A stable foamprecursor was formed in each instance.

Stable foams were prepared from each one of the foam precursors preparedusing the acids disclosed in runs 1 through 6 according to the followingprocedure:

To the total quantity of each foam precursor prepared as indicated inExample IV and Table III were mixed without the addition of externalheat or pressure 50 grams of propylene oxide adduct of sucrose having amolecular weight of 1,200 and an equivalent weight of 125. To thismixture were added 2 grams of siloxane-polyglycol block copolymersilicon oil, 1 gram dibutyl tin diacetate and 20 grams oftrichlorofiuoromethane. Upon addition of the polyol the foam began toform. A flame-resistant non-burning foam was formed.

Example V First, a stable foam precursor was prepared comprising: 100parts of polymethylene polyphenylisocyanate having a molecular weight of400, an equivalent weight of 134 and a functionality of 3, 55.0 parts oftrimellitic acid anhydride and 25.0 parts of trichlorofiuoromethane.

The mixing was continued until all of the trimellitic anhydride had beencompletely dispersed. It should be noted that the order of addition isnot critical to the invention.

In the above mixture the weight ratio of the polymethylenepolyphenylisocyanate to trimellitic acid anhydride totrichlorofiuoromethane is 1015.5 22.5. This foam precursor was aged for14 weeks. At the end of this period 180 parts of this foam precursorwere mixed without addition of external heat or pressure with 45 partsof the propylene oxide adduct of sucrose having a molecular weight of1,200 and an equivalent weight of 125 in the presence of 3 parts ofsiloxane-polyglycoi block copolymer silicon oil and 2.5 parts oftrichlorofiuoromethane. Upon the addition of the poiyol foam began toform. A flame-resistant non-burning foam was formed.

Example VI First, a stable foam precursor was prepared comprising: 100parts of polymethylene polyphenylisocyanate having a molecular weight of400, an equivalent weight of 134 and a functionality of 3, 55.0 parts oftrimellitic acid anhydride and 30 parts of trichlorofiuoromethane. Themixing was continued until all of the trimellitic anhydride had beencompletely dispersed.

In the above mixture the weight ratio of the polymethylenepolyphenylisocyanate to trimellitic acid anhydride totrichlorofiuoromethane is 10:5.5:3.0. This foam precursor was aged for12 months. At the end of this period 185 parts of this foam precursorwere mixed without addition of external heat or pressure with 45 partsof the propylene oxide adduct of sucrose having a molecular weight of1,200 and an equivalent weight of in the presence of 3.0 parts ofsiloxane-polyglycol block copolymer silicon oil and 10.0 parts oftrichlorofiuoromethane. Upon the addition of the polyol, foam began toform. A flame-resistant non-burning foam was formed.

We claim:

1. As a composition of matter a stabilized liquid nonpolymeric foamprecursor prepared by mixing:

(a) a fluorine substituted halogenated alkane having a carbon chainlength of 1 6 carbon atoms and boiling above 60 F.; and

(b) a liquid polyarylpolyisocyanate which polyarylpolyisocyanatecontains at least two interconnected aromatic rings having at least oneisocyanato group per aromatic ring; and

(c) an aromatic carboxylic acid derivative comprising an aromaticnucleus substituted by at least two members selected from the groupconsisting of carboxyl, dicarboxylic anhydride and acyl halide; whereinthe molar ratio of said aromatic carboxylic acid derivative to thepolyarylpolyisocyanate is 1:5 to 2.33:1 and wherein the fluorocarboncontent is 1-20 percent by weight of the total foam precursorcomposition.

2. The composition of claim 1 wherein the polyarylpolyisocyanate ispolymethylene polyphenylisocyanate.

3. The composition of claim 1 wherein the fluorine substitutedhalogented alkane is trichlorofiuoromethane. 4. The composition of claim1 wherein the aromatic carboxylic acid derivative is trimellitic acidanhydride. 5. The composition of claim 1 wherein said molar ratio isbetween about 1:5 to about 1:1.

References Cited Rigid Urethane Foams-II Chemistry and Formulation,bulletin of E. l du Pont de Nemours and Co., Bulletin No. HR-26, April1958, pp. 13, 14, and front cover.

HOSEA E. TAYLOR, Primary Examiner M. J. WELSH, Assistant Examiner U.S.Cl. X.R.

